Apex were pleased to receive “Highly Commended” in the sound insulation category of the Association of Noise Consultants’ Awards 2016. The Vermont ApartHotel required the development of a timber floor detail that overcomes the inherent problem of low-frequency footfall noise with lightweight floors.
The inadequacy of conventional impact sound descriptors to correlate with occupants’ experience was widely known within the UK community of acoustic consultants, but better descriptors were not. The research included an international literature review, which linked for the first time separate initiatives across Europe, Asia and the USA to address this problem. This is an emerging area of research, and we found when we contacted people that many were unaware of the developments undertaken by others on different continents. We presented the research at the Institute of Acoustics’ annual conference in Harrogate 2015; this has galvanised the industry into taking action to address the problems inherent in the current Building Regulations assessment.
The future occupants may be either on business or enjoying a stag / hen weekend, or a romantic break. The range of potential occupants therefore has the potential to generate high levels of impact sound, and also to be very sensitive to intrusive impact sound. This means that a very high performance for impact sound insulation was required. It was known that the Building Regulations in England not only provide poor protection against impact sound, but also that the metric adopted in Approved Document E provides only limited correlation with user experience for lightweight floors. Floor impact sound has been reported as the most irritating noise source in timber frame residential buildings, according to Sato et al.
The most significant sources of information correlating occupant satisfaction with different performance parameters and values included:
- The COST-TU0901 programme, being developed as ISO/NP 19488 acoustic classification system].
- The Akulite criteria, developed as a result of a ten year Swedish research programme, and recently adopted by the Swedish Standard SS 25267 (English version coming soon!) in their acoustic classification system.
- The Low-frequency Impact Rating (LIR), proposed by LoVerde and Dong, in the USA.
- The new impact test with a soft heavy ball described in ISO 10140-3, Annexe A to determine LAF,max levels, and proposed classification schemes.
This project is a fantastic example of consultancy work spawning research that inspires entirely novel construction solutions. The pioneering and innovative work concerned the development of a suitable separating floor detail between apartments. The detail developed has extensive potential applications in new-build timber flats as well as refurbishment projects; it is proven to offer the highest Class of impact sound insulation under the ISO Acoustic Classification System currently under development. This represents a significant advance on current lightweight timber frame floating floor technology, which cannot achieve this performance.
There were limited options for remodelling but the client sought high standards of sound insulation along with retention of the timber joist floors and provision of underfloor heating. The client was especially concerned about footfall noise, and was keen that this would not be intrusive. The research revealed the inherent limitations of entirely lightweight solutions. When presented with a variety of options, the client did not chose the solution with the best possible impact sound performance; they chose the one that offered the most cost effective and buildable solution with the best balance of performance.
Imran Khaliq, Gainford Group (client), remarked:
When we took on the re-development of this listed building, we were concerned about avoiding problems with impact noise through the floors. We have had problems in other developments with timber floors, and it was important in this luxury apart-hotel that people would not be able to hear noise from people walking about over their heads.
We always look to Apex on all matters of acoustics and noise, because they always provide us with practical advice on cost-effective solutions. They didn’t let us down here, with their “out of the box” solution for the floor detail. We had to get the buy in from the acoustic membrane people that their product was suitable to be used in this way on a timber floor. The result was a straight forward design that was easy to build and achieves fantastic results. Thank you Apex.